A handy online comparison of several different brands may be found here.

You're going, wait, I called 'em Legos as a kid. LEGO is the brand name, and enthusiasts insist that LEGO is both singular & plural. If you use the word Legos you're seen as a noob. On this site, no matter the manufacturer, we call 'em bricks. They're all ABS plastic, they're all going to be glued together with ABS cement, they're all going to become part of an AR lower.

One of the problems with the AR lower is the rear of the lower, between the rear upper lug pin and the bottom of the buffer tube. This is where improperly spec'd lowers break. The Marine Corps recognized this in 1982, and hence the M16A2 lower receiver is reinforced in that area, as opposed to a M16A1 receiver. We've seen the same problem with improperly spec'd aluminum AR receivers, and repeated failures of plastic receivers at that same point, including during the development of Defense Distributed's 3-D printed lower.

Cavalry Arms, the original plastic lower manufacturer in 2000, solved that problem by incorporating the stock into the lower design. Thus, the stock reinforces the weak part of the lower. We'll do the same thing. Our first major effort, Effort Thumbhole, is an attempt to build an AR compatible thumbhole stock out of bricks. Why out of bricks? Because at the moment on the US market, there is no new production thumbhole stock that we're aware of, and we view this reinforcement as necessary before we proceed onto Effort Bloomberg that will produce the lower.

If someone is a stock designer, feel free to take over Effort Woodstock, and we'll happily use a wood thumbhole stock instead of a brick one. Someone is supplying New Zealanders with a thumbhole stock, if we could just get 'em to tell us who makes it, we'll buy some. (Er, they do, and apparently they're made of unaffordium - though slightly cheaper than Ze Jermans. See Effort Woodstock.)

On to Effort Bloomberg. This is the meat of the Feinstein Project, and the hardest part. Why so difficult? We'd like to line up all the holes - both upper lugs, trigger, hammer, and safety - without drilling. That's going to be very difficult to do, as bricks don't just have holes in random places - they're in very specific places, as are the holes in an AR lower. The magazine well, as the Virginian has shown us, is a bit easier - you saw & file until the magazine fits. Triggers? Not so easy.

The buffer tube is easier in this project than if you built a lower on your mill at home. Why? Because we're not going to tap the lower to screw the buffer tube in. We're going to screw it, glue it, or otherwise affix it into the thumbhole stock, and the stock is going to line the buffer tube up for us. If worst comes to worst, we'll use a full length buffer tube, cut the solid end off, and install it backwards, screwing it into a shotgun or AK/AR stock adapter.

The magazine well may prove to be the easiest of all. Due to the ubiquity of AR magazines and the politicians who encourage their use by threatening to ban them, there are quite a number of AR compatible magazine well conversions for various rifles. They run from outlandishly expensive to AirSoft pricing, 'cause, er, well, they're AirSoft. (This is a plastic lower - we're not turning down plastic AirSoft parts that fit because they're plastic.) We have a G36 AirSoft mag well on order, and after we cut out the CO2 bits we'll see if our Cammenga mags fit. (They do - see Sub Effort G36)

The holy grail of mag well adapters would be the LE901-16S Conversion Kit. Not only is it a near complete AR magwell, it has the upper front lug pin holes machined in aluminum by Colt machinists. It's one-third of an AR lower, complete. Which means it'll be ridiculously expensive (We were right! $294!). Hmm - wonder if we could get Defense Distributed to print some...

You're thinking, well, it's possible, but the gubbermint will just ban it. Maybe. We fully expect the People's Republic of California to pass a bill named after this project. recondodan was the first to utter the immortal words: